how much space to leave on a ssd?

sims 3 no matter what specs u give it seems to lag alot like im playing on a 1650s and i59400 which should be more than enough for this game and i still get lag spikes sometimes but nat as bad as my old ancient laptop lol.

i followed this guide here https://steamcommunity.com/sharedfiles/filedetails/?id=1131162350 srsly life changer of a guide improves the sims 3 significantly